Convert Snake Case to Camel Case

Convert a lowercase snake-case string to lower camel case. Keep the first nonempty component lowercase, capitalize the first letter of each later nonempty component, and remove every underscore. Consecutive, leading, and trailing underscores are allowed.

Function
snakeToCamelCase(snake: String) → String

Examples
Example 1
snake = "hello_world"
return = "helloWorld"
The later component begins with an uppercase letter.
Example 2
snake = "one_two_three"
return = "oneTwoThree"
Every later component is capitalized.

Constraints
0 <= snake.length <= 100000
snake contains lowercase English letters and underscores.

The trick is a single left-to-right pass with one boolean flag, call it capitalizeNext. Start it as false and track whether you've emitted any character yet. For each character: if it's an underscore, set the flag to true and skip it. Otherwise, if the output is empty, append it as is, because the first nonempty component stays lowercase. If the output isn't empty and the flag is set, append the uppercase version and clear the flag. Else append it as is. The pitfall is leading underscores. If you set the flag on a leading underscore and don't check for an empty output, you'll capitalize the first component and fail. Use a list or StringBuilder, not repeated string concatenation, since length goes up to 100000. That's O(n) time. If you blank on the flag logic during the live OA, StealthCoder is your hedge.

If this hits your live OA and you blank, StealthCoder solves it in seconds, invisible to the proctor.